Designed and built by the Nambu
Arms Manufacturing Company, the Type 100 was a robust, if unremarkable,
submachine gun that was first delivered to the Imperial
Army, in 1942. Japan was surprisingly late to introduce the submachine gun
to its armed forces.

The Type 100 was a well made gun, but the 8x22mm
Nambu round was underpowered, roughly the equivalent to the .380 ACP.
Atypically for a submachine gun but typical of Japanese small arms, a bayonet
lug was fixed under the barrel.

Despite its shortcomings and complexities, the Type 100 had a high quality chrome
plated barrel to aid cleaning and reduce wear. Some models also featured a bipod
or a complicated muzzle
brake.